Aircraft sustaining rotor



0d. 15, 1940- J. A. BENNETT AIRCRAFT SUSTAINING ROTQR original Fileduarch 51, 193s sheets-sheet `1` 'I INVENTOR Wfm I' v ATTORNEYJ.

Patented Oct. 15, 1940 UNITED STATES AIRCRAFT SUSTAINING ROTOR James Allan Jamieson Bennett, Esher, England, assigner, by mesne assignments, to Autogirov Company of America, a corporation of Delaware Application March 31,

1938, Serial No. 199,150(

Renewed July 13, 1939. In Great Britain April 18 Claims.

This invention relates to aircraft sustainingv rotors, and is particularly concerned with the type of rotor incorporating one or more blades which are articulated to a common generally upright hub, the blades being arranged to provide for autorotative actuation in ilight.

Still further, the invention has particular reference to rotors of this general type which are also arranged to be driven on the ground prior to m take-oil in order to store kinetic energy in the rotor, the blade pitch angle at this time being at a low, preferably zero, value, so that upon disconnection of the drive and raising of the pitch angle, a high initial thrust is secured to effect 1s direct or jump take-oil.

The invention contemplates a blade articulaltion and rotor driving arrangement for the above purpose, and in considering some of the ativantages it should be noted that in certain prior conzo structions change of pitch as between the zero and :Ilight positions is provided for by employing a blade pivot the axis of which is inclined upwardly and outwardly with respect to the longitudinal blade axis, so that upon application of the driving torque, the blade assumed a lagging and low pitch position, and, upon cessation of the driving torque, the blade advanced to the radial' or to a leading position in which the pitch was increased. Such a construction is disclosed in copending application of Juan de la Cierva, Serial No. 738,349, filed August 3, 1934, corresponding to British Patent No. 420,322, accepted November 29, 1934. As may be seen in that case, thev inclined pivots may desirably be provided with lagging and leading stops limiting the range of pitch change movement.

In arrangements of said prior type, if thek oblique pivot is inclined at an extreme acute angle to the blade and is utilized during normal flight operation to accommodatelag and lead displacements of the blade, the blade oscillations are unstable, at least in the absence of damper devices.

The present invention provides blade pivots including a napping or delta pivot which is acutely angled with respect to the longitudinal Iblade axis at the leading side thereof to provide for pitch change of the blade during apping, and also a drag or alpha-pivothaving its axis so positioned as to produce a stable condition, the lag and lead displacements of the blade about this pivot being aerodynamically damped.

The invention further provides a drive mechanism having a driving element extended to engage a blade pivot part in such manner as to ensure that the blade will move on the alpha pivot 55 axis to a low or zero pitch position during driving.

How the foregoing objects and vadvantages are attained, will appear more fully in the following description making reference to the accompanying drawings, in Which- Figure 1 is a top plan View of a rotor hub and thet root ends of three blades articulated thereto by means of pivots constructed in accordance with the invention;

Figure 2 is a vertical sectional view of the structure shown in Figure 1; and i Figure 3 is a view taken substantiallyas indicated by the section line 3 3 applied to Figure v1.

For purposes of control of the craft in flight, the rotor here shown is mounted for tilting in all directions by means of a gm-bal ring 5 adapted to be trunnioned as at 6 6 on any suitable rotor hub support or xedpylon structure. The hub is carried within the ring 5 by means of additional trunnions T T, the axis of which is at right angles to the axis of the trunnion 3 6. The manual control for rotor tilting need not here be shown as suitable control for this purpose appears in the copending Cierva application above referred to.

'Ihe trunnions 'I 'I carry downwardly-and inwardly extended rotor hub-supports 8 3 which serve to mount the non-rotative bearing housing I in which a rotative hub spindle III is journalled as by bearings II. A block or hub proper I 2 is connected to the upper end. of the rotative spindle Il, this hub block having three radially extended ilapping pivots I3 which cooperate respectively with the several blades, the root end portion of the blade spars appearingat I4 in Figure 1.

Each spindle or apping pivot I3 serves to carry the intermediate member I5 which is journalled thereon, a thrust bearing I6 interposed between the member I5 and the abutment I1 serving to take loads axially of the flapping pivot I3.

The intermediate member I5 for each blade carries pivot I 8 (the alpha or drag pivot) on which the gooseneck blade connecting member I9 is journalled, the latter being in turn connected with the blade spar I4. The several parts just'described are so positioned as to bring the longitudinal axis of the blade to aposition in which it substantially intersects the rotational axis of the hub.

Inspection of the several figures of the drawings will show that 'the axis d d of the flapping or delta pivot I3, when viewed in plan, makes an acute angle with the longitudinal axis of the blade'B-B at the leading edge thereof, the direction of rotation being indicated by an arrow. It will also be noted from Figure l that the axis d d is slightly oiiset from the axis ofv rotation drive and its cooperation with the pivot o! the hub, and that the axis a--a of the alpha or drag pivot is offset from the hub further than the axis tif-d.

Still further. ,as best seen in Figure 3, the axis af-a of the alpha or drag pivot. when projected on a plane perpendicular to the blade axis, makes an acute angle Wlththe hub axis R--R. `A sec ondary inclination of the alpha axis appears when viewing the rotor in plan, as in Figure 1, in which it will be seen that the axis of this pivot makes an acute angle with the longitudinal blade axis B-B at the trailing side thereof.

Turning now to the driving mechanism, a centrally located drive shaft 20 is connected by means of universal joint 2l with the lower part 22 of a disengageable clutch, the upperpart 23 of which is disposed at the lower endoffa fihollow shaft 24 serving, as a guideforllongitudinal movement of the* sleeve f 25 .which projects :upwardly vfrom the lowerl part, of- -thegzclutch` 22. Shaft 24 extends 'upwardly 'through the rotative spindle I0, and toward its upper end carries a series of rollers 26 adapted to engage respectively with arms 21 formed on the root end fittings I9 of the several blades. 'I'he operation of. this A axes is described hereinafter. i

It may first be noted that becauseof the inthereof and increase of blade pitch upon down- A`ward flapping. movement, and a drag pivot for the blade positioned to provide for pitch change cllnation of the alpha pivot .axis with respect to the longitudinal axis of the blade, as seen injf' Figure 2, lagging displacement of the bladeitbout this axis decreases the pitch and `leading displacement increases the pitch.- Therefore, upon'. application of 'the drivingftorque to the rotor'-4 hub, even without the provision of special drivem; mechanism, the resultlng'lag of the bladepr'oy and a blade, a flapping pivot for connecting the duces a decrease in pitch'. However. in-'order to ensure'that the blade shall be held againstK the lagging stop and thus at zero pitch; drive mechanism of the character described abovev is pref rably employed, this drive mechanism trans'- mit ng torque directly to the blade root con-v By virtue of the inclination of the alpha pivot axis when projected on a plane perpendicular. to the blade axis (i. e. making an acute angle with the axis of the hub), the lag and lead movements of the blade in flight operation produce components of motion in the flapping sense and therefore are aerodynamically damped, thus overcoming instability heretofore encountered in some arrangements of this general type.

The provision of an obliquely angled flapping pivot in combination with the alpha pivot 1nclination above discussed, s of advantage since, in purely leading and lagging displacements of the blade, the flapping component of the movement on the alpha pivot is compensated by a flapping displacement of opposite sign on the delta pivot Which because of the Obliquity of the latter produces a variation of blade angle, a decrease of blade anfgle by pivotation about the delta pivot being associated with a lagging displacement about the alpha pivot.

The inclinations of the delta and alpha pivot axes as described, and the mounting of the blade, provide for substantially zero blade pitch when the blade is against the lagging stop and extended in a substantially horizontal position. Maintenance of the substantially horizontal position is assured at high R. P. M. by thefact that the centrifugal force is large compared with the weight of the blade, and further by the fact that the flapping movement is stabilizedby the inclination of the delta axis iny a sense causing the blade angle to decrease with upward flapping, and vice versa.

'I'he inclination of the delta axis in the direction stated has still other advantages, including improvement in smoothness of flight operation,

especially in rough air, and also improvement y with respect to the lift-vector-shift characteristic, as disclosed in copending application Serial No. 199,151, led March 31, 1938, issued March 5, 1940 as Patent No. 2,192,492, corresponding to British application No. 9801, filed April 6, 1937.

I claim:

l. In an aircraft sustaining rotor having a hub and a blade, a flapping pivot for connecting the blade with the hub and obliquely inclined with respect to the blade axis to provide for decrease of blade .pitch upon upward flapping movement movement thereof, the axis of the drag pivot, when projected on a plane perpendicular to the blade axis, making an acute angle with the axis of the hub.-

'I 2. In an aircraft sustaining rotor having a hub .b lade'with the hub and obliquely inclined with -respec-t to the blade axis to provide for decrease of vblade pitchA upon upward flapping movement thereof andl 'increase of blade pitch upon downward flapping movement, and a drag pivot for the blade positioned to provide for pitch change movement thereof, the axis of the drag pivot being' inclined upwardly and rearwardly of the 3. In an aircraft sustaining rotor having a hub and a blade, a flapping pivot Ifor connecting the blade with the hub and obliquely inclined with respect to the blade axis to provide for decrease of blade pitch upon upward flapping movement thereof and increase of blade pitch upon down'- ward` flapping movement, a drag pivot for the .blade positioned to provide for pitch change movement thereof, the axis of the drag pivot,

blade axis, making an acute angle with the axis of the hub, and drive mechanism for the rotor 1ongitudina1 axis of the made at the1eading side f 55 when projected on a plane perpendicular to the j longitudinal ax'ls of the blade, one at the lead- 'c5 a hub and a blade, pivot mechanism for connecting the blade to the hub including apivot progitudinal axis of the bladeat the leading side thereof, and a second pivot axis accommodating lag and lead movements of the :bladewhich second pivot axis', when viewed 'in plan, makes an.v

acute angle with 4the longitudinal bladeaxis'at the trailing edge thereof, the axis ofthe second pivot being inclined upwardly and rearwardly 0f. the blade.

6. In an aircraft sustaining rotor incorporating a hub and a blade, pivot mechanism for connect'- ing the blade to the hub including a pivot providing for upward and downward napping movement of the blade and, when viewed in plan, arranged with its axis atan acute angle to the. longitudinal axis of the blade at the leading side thereof, and a second pivot axis accommodating lag and lead movements ofthe blade, which second pivot'axis, when viewed in plan, makes an acute angle with the longitudinal blade axisat the trailing edge'thereof, both of said pivot axes being offset from the axis of the hub.

7. In an aircraft sustaining rotor incorporating a hub and a blade, pivot mechanism for connecting the bladeto the hub including a pivot providing for upward and downward flapping movement of the yblade and, when viewed in plan, arranged with its axis at an acute angle to the longitudinal axis of the blade at the leading side thereof, a second pivot axis accommodating lag and lead movements of the blade, which second pivot axis, when viewed in plan, makes an acute angle with the longitudinal blade axis at the trailing edge thereof, and driving mechanism for the rotor including a driving connection extended to engage a part movable with the blade about the second pivot axis and providing for movement of the blade about said second pivot axis to a reduced pitch position upon application 0f the drive.

8. In'an aircraft sustaining rotor having a hub and a blade, pivot mechanism connecting the blade with the hub including two pivots both obliquely inclined with respect to the longitudinal axis of the blade to provide for pitch change movement, the axes of said two pivots, when viewed in plan, making acute angles with the longitudinal axis of the blade, one at the leading edge thereof andthe other at the trailingfedge thereof, and at least one of said axis lying ap-` proximately in a plane perpendicular to the hub axis.

l9. In an aircraft sustaining rotor having a hub and a blade, pivot mechanism connecting the blade with the hub including two pivots both obliquely inclined with respect to the longitudinal axis of the blade to provide for pitch change movement, the axes of said two pivots, when viewed in plan, making acute angles with the ing edge thereof and the other at the trailing edge thereof, at least one of said axes lying approximately in a plane .perpendicular to the hub axis, and drive mechanism for the rotor cooperating with a blade pivot part tol deliver torque thereto in a sense providing for decrease of blade pitch about one of said pivots uponl application of the driving torque.

10. In an aircraft sustaining rotor having a hub and a blade, pivot mechanism for connecting the blade with the hub including a apping pivot providing Primarily for movement of the blade in a direction transverse its mean rotative path of travel, and a second pivot the axis of which, when viewed in plan, is acutely angled with respect to the longitudinal blade axis at the trailing edge thereof and which is inclined upwardly and rearwardly with respect to the blade,

the second pivot providing for lagging and leading displacement of the blade from a true radial position.

11. In an aircraft sustaining rotor having a hub and a blade, a flapping pivot for connecting the blade with the hub and obliquely inclined,l

with respect to the blade axis to provide for decrease of blade pitch upon upward flapping movement thereof and increase of blade pitchv upon downward flapping movement, and a drag pivot for the blade positioned to provide for pitch change movement thereof, the axis of the drag pivot being spacedv further from the .axis of the hub than the axis of the flapping pivot and, when projected on a plane perpendicular to the blade axis, making an acute angle with the axis of the hub.

12a. In an aircraft sustaining rotor having a hub and a blade, a flapping pivot for connecting the blade with the hub and obliquely inclined with respect to the blade axis to provide for decrease of blade pitch upon upward flapping movement thereof and increase of blade pitch upon downward flapping movement, and va. drag pivot for the blade positioned to provide for pitch change movement thereof, the axis of the drag pivot being spaced further from the axis of the hub than the axis of the flapping pivot and inclined upwardly and rearwardly of the blade.

13. In .an aircraft sustaining rotor having a hub and a blade, 'a flapping pivot for connecting the .blade with the hub and obliquely inclinedwith respect to the blade'axis to provide for decrease of blade pitch upon upward flapping movement thereof and increase of blade pitch upon downward flapping movement, a drag pivot for the blade positioned to provide for pitch change movement thereof, the axis of the drag pivot be ing spaced further from the axis of the hub than the axis of the fiappingpivot and when `projected on a plane perpendicular to the blade axis, making .an acute angle with the axis ofthe hub, and drive mechanism for the rotor connected with a blade pivot part in such manner as to cause the blade to move about the axis of the second pivotin a direction to decreasethe. pitch thereof. I

14. Inan aircraft sustaining rotor havingr ay hub and a blade, pivot mechanism for connecting the blade with the hub including a flapping pivot providing primarily for movement of the blade in a direction transverse its mean rotative path of travel, and a second pivot the axis of which, when v iewed in plan, is acutely angled with respect to the longitudinal blade axis at the trailing edge thereof and which is inclined upwardly and rearwardly with respect to the blade and is spaced further from the axis ofthe'hub than the axis of the apping'pivot, thesecond pivot providing for lagging' .and leading 4displacement of the blade from a true radial position.

15. In an aircraft sustaining rotor, a hub, three blades positioned with their longitudinal axes radiating from the hub, pivot means for connecting the blades with the hub including pivot parts clustered around the hub in positions intermediate the longitudinal axes of the blades, the pivot means for each blade including a flapping pivot the'axis of which when viewed in plan makes an acute angle with the longitudinal axis of the blade and a drag pivot the axis of which is positioned to provide a component of blade movement in the pitch-change sense, the axis of the flapping pvot lying close to a position of coincidence with the longitudinal axis of an adjacent blade but being slightly offset from the hub axis, and the axis of the drag pivot being oiset from the hub axis a distance greater than the offset of the flapping pivot axis.

16. In an aircraft sustaining rotor having a hub and a blade, pivot mechanism connecting the hub with the blade including a pivot having its axis positioned to provide primarily for flapping movement of the blade, and a pivot having its axis positioned to provide primarily for lag-lead movement of the blade, the flapping pivot axis, when viewed in plan, making an acute angle with the longitudinal axis of the blade at the leading side of the latter, the axes of both of said pivots being offset from the hub axis, and the lag-lead pivot axis being offset from the hub axis to an extent greater than the flapping pivot axis.

17. In an aircraft sustaining rotor having a hub and a blade, pivot mechanism connecting the hub with the blade including a plvothaving its axis positioned to provide primarily for flapping movement of the blade, and a pivot having its axis positioned to provide primarily for lag-lead movement of the blade but obliquely inclined with respect to the longitudinal axis of the blade to provide a component of blade movement in the pitch-change sense, the flapping pivot axis, when viewed in plan, making an acute angle with the longitudinal axis of the blade at the leading side of the latter, the axes of both of said pivots being offset from the hub axis, and the lag-lead pivot axis being offset from the hub axis to an extent greater than the flapping pivot axis.

18. In an aircraft sustaining rotor having a hub and a blade arranged with its longitudinal axis substantially intersecting the hub axis, pivot mechanism for connectng the blade with the hub including a flapping pivot oilset forwardly of the longitudinal blade axis, the axis of which pivot, when viewed in plan, makes an acute angle with the longitudinal blade axis at the leading side thereof, and a drag pivot operatively interposed between said flapping pivot and the blade, the drag pivot being obliquely inclined with respect to the longitudinal blade axis and providing for decrease of blade pitch upon lagging movement of the blade and increase of pitch upon leading movement thereof, and driving mechanism for the rotor including a driving element movable with respect to. and cooperating with a part of the blade pivot mechanism for urging the blade to move upon one of said pivots in a sense effecting decrease of blade pitch upon application of torque.

JAMES ALLAN JAMIESON BENNETT.

CII 

